1. Field of the Invention
This invention relates to a method of forming iridium- or iridium-containing materials on substrates, such as Ir-based electrode structures for microelectronic devices and subassemblies, as well as to Ir source reagent materials, and novel dielectric capacitor or ferroelectric material device structures.
2. Description of the Related Art
Iridium (Ir) and iridium oxide (IrO2) are of great interest for use as electrode materials in both dynamic random access memories (DRAMs) and for ferroelectric-based memory devices (FRAMs) which incorporate perovskite metal oxide thin-films as the capacitor layer.
The advantages of Ir over other possible electrode materials include ease of deposition, the ability to xe2x80x9cdry etchxe2x80x9d the material, the ability to form a stable conducting oxide at high temperatures in an oxidizing environment, and the ability to operate reliably at high temperatures in a working device.
The deposition and processing of Ir-based electrodes is highly desirable in view of the aforementioned advantages. Further, the formation of IrO2 acts as a diffusion barrier to oxidation of conducting polysilicon vias or plugs, as is required in high density DRAM or FRAM devices.
Based on the need for Ir-based electrodes, the art has continued to seek improvements in source materials and deposition techniques for the formation of Ir-based films.
The art has variously disclosed the chemical vapor deposition of iridium for the manufacture of electronic devices in a reducing atmosphere, such as hydrogen gas environment. The art has taught the use of such reducing atmosphere for the purpose of achieving the deposition of element metal iridium for electrodes in applications in which high temperature dielectric materials (e.g., SBT, BST, PZT, PLZT, PNZT, LaCaMnO3, etc., wherein SBT =strontium bismuth tantalate, BST =barium strontium titanate, PZT =lead zironium titanate, PLZT =lead lanthanum zirconium titanate, PNZT =lead niobium zirconium titanate) are deposited on the electrode, to minimize the possibility of degradation of the dielectric in such applications and to concurrently achieve the formation of high purity metal.
The art has especially sought improvements in process technology for the formation of semiconductor and ferroelectric structures that employ Ir electrodes specifically associated with complex dielectric or ferroelectric material layers as thin-film capacitors.
It is an object of the present invention to provide novel source reagents and a process for the formation of iridium-based electrodes that achieve a material simplification in fabrication efficiency and cost, and provide an electrode structure that is highly advantageous for integration with silicon device technology, being efficient, oxygen reactive, oxygen impermeable, and readily fabricated.
It is another object of the invention to provide a simplified method for the fabrication of metal oxide thin film capacitor structures including iridium, iridium oxide or iridium-containing electrode elements, as metal contacts for the oxide DRAM and FRAM devices.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.
This invention relates to a method of forming iridium- or iridium-containing materials on substrates, such as Ir-based electrode structures for microelectronic devices and subassemblies, and catalytic materials, as well as to Ir source reagent materials, and novel dielectric material structures.
As used herein, the term xe2x80x9cIr-basedxe2x80x9d or xe2x80x9ciridium-basedxe2x80x9d refers broadly to elemental iridium, iridium oxide, iridium-containing material compositions and combinations thereof.
The present invention also relates to novel high temperature dielectric or ferroelectric thin film capacitor structures including Ir-based electrode elements.
In one aspect, the invention relates to a method of forming an iridium-containing film on a substrate, from an iridium-containing precursor thereof that is decomposed to deposit iridium on the substrate, such method comprising decomposing the precursor and depositing iridium on the substrate in an oxidizing ambient environment. The deposition of iridium on the substrate may be carried out in any suitable manner and by any appropriate techniques of the art, including chemical vapor deposition (CVD), assisted CVD, or physical deposition methods such as ion plating, rapid thermal processing, molecular beam epitaxy, etc.
As used herein, the term xe2x80x9coxidizing ambient environmentxe2x80x9d means an environment including oxygen-containing gas, such as oxygen, ozone, air, nitrogen oxide (NOx), or the like. Such oxidizing atmosphere may be provided in a deposition chamber or reaction vessel in which the deposition is carried out, and enables the formation of iridium or iridium oxide on the substrate. Accordingly, the deposition may be conducted in an ambient air environment, thereby simplifying the formation of the iridium-containing film on the substrate. In an alternate embodiment, IrO2 may be formed in a post-deposition process from Ir metal by treatment in an oxidizing environment.
The Ir precursor material may be of any suitable composition and type. In preferred practice of the present invention, the precursor may suitably comprise a Lewis base-stabilized xcex2-diketonate iridium composition or a Lewis base-stabilized beta-ketoiminate composition, as hereafter more fully described.
When the iridium-containing film is employed to form an electrode or other patterned structure on the substrate, the deposited iridium or iridium oxide film may be dry etched with a halogen-based plasma and/or preferably, XeF2, as more fully described in concurrently filed U.S. patent application Ser. No. 08/966,796 filed Nov. 10, 1997 now U.S. Pat. No. 6,018,065 in the names of Thomas H. Baum and Frank DiMeo, Jr., for xe2x80x9cMethod for Etch Fabrication of Iridium-Based Electrode Structures,xe2x80x9d the disclosure of which hereby is incorporated herein in its entirety. In such dry etching of a deposited iridium or iridium oxide film, the etch rates can optionally be enhanced through the use of Lewis-based adducts or electron back-bonding species such as carbon monoxide, trifluorophosphine, trialkylphosphines or other suitable Lewis base.
In yet another aspect of the present invention, the iridium-containing film subsequent to its formation as an electrode structure may have deposited thereon a high temperature dielectric and/or ferroelectric material. An oxidizing ambient environment may be employed for the deposition of the iridium-containing film or may be used solely during the deposition of the oxide dielectric/ferroelectric.
It may therefore be unnecessary to purge the chamber of a reducing atmosphere, or to transfer the substrate article bearing the iridium-containing film from the iridium deposition chamber to a dielectric/ferroelectric deposition chamber, as has been done in the prior art to accommodate the usage of hydrogen or other reducing gas (forming gas) atmospheres in the iridium electrode formation step.
The method of this invention therefore achieves a substantial simplification of the procedure for forming a capacitor or other microelectronic device in which the iridium-containing electrode is overcoated with a dielectric or ferroelectric material.
Another aspect of the invention relates to a microelectronic device structure comprising an iridium oxide electrode element overcoated by a high temperature dielectric, e.g., SBT, PZT, BST, PLZT, PNZT, LaCaMnO3, etc., wherein the electrode is conductively operative in relation to the high temperature dielectric. As used herein, high temperature dielectric refers to a dielectric material deposited on the electrode at a temperature above about 300xc2x0 C. By way of example, dielectric films of lead zirconium titanate (PZT) are typically deposited at temperatures on the order of 500-600xc2x0 C.
Yet another aspect of the invention relates to a composition comprising an organic solvent solution of an Ir(I) reagent, wherein the Ir(I) reagent is selected from the group consisting of:
Lewis base stabilized Ir(I) xcex2-diketonates of formula I: 
xe2x80x83wherein R and Rxe2x80x2 may be alike or different and may be H, aryl, perfluoroaryl, C1-C6 alkyl, or C1-C6 perfluoroalkyl, and L is a coordinating Lewis base; and
Lewis base stabilized Ir(I) xcex2-ketoiminates of formula II: 
xe2x80x83wherein R, Rxe2x80x2, and Rxe2x80x3 are the same or different, and are independently selected from the group consisting of H, aryl, perfluoroaryl, C1-C6 alkyl, or C1-C6 perfluoroalkyl, and L is a coordinating Lewis base; and
the organic solvent solution comprises a non-polar solvent, such as C5-C12 hydrocarbon alkanes (e.g., hexane, heptane, octane, nonane and decane) and C6-C10 hydrocarbon aryls (e.g., benzene, toluene and xylene).
Yet another aspect of the invention relates to a composition comprising a non-polar solvent solution of a cyclooctadiene (COD) adduct of an Ir(I) beta-diketonate.